The present invention relates to a shift arrangement for a motor vehicle transmission which has at least two gear stages, which can be engaged and disengaged by means of different rods.
The present invention furthermore relates to a method for actuating a shift arrangement of a motor vehicle transmission which has at least two gear stages.
Shift arrangements of this kind are known in the prior art. In general, a motor vehicle transmission has one shift clutch pack for every two gear stages, said pack consisting of two shift clutches, which can be actuated by means of a common sliding sleeve. In this case, the shift clutches can be claw clutches but are preferably synchronizing shift clutches. The motor vehicle transmission is preferably a spur gear transmission of layshaft construction.
In a conventional shift arrangement, each sliding sleeve is coupled to a shift rod. The shift rods each have grooves, in which a shift finger fixed on a shift shaft can engage. Here, the shift shaft can be arranged parallel to the shift rods. In this case, turning the shift shaft leads to a selecting operation, in which a particular shift rod is selected, and longitudinal movement of the shift shaft leads to a shifting operation, in which a shift clutch associated with the shift rod is actuated. Arranging the shift shaft transversely to such shift rods is also known. In this case, selecting is performed by a longitudinal movement of the shift shaft, and the shifting operation is initiated by a process of turning the shift shaft.
Equipping shift shafts with a plurality of shift fingers, each assigned to one shift fork, is also known. The shift forks each engage in associated sliding sleeves of shift clutch packs. Here, the shift rod is generally moved axially for shifting and is turned to select a shift fork. Providing each shift clutch on a shift shaft of this kind with a plurality of shift fingers arranged axially offset one behind the other is also known in this context. This makes it possible to leave one gear stage engaged and to engage a further gear stage. This is relevant particularly in the area of dual clutch transmissions. Dual clutch transmissions have two transmission sections, of which in each case one is used actively for power transmission and the other is inactive. A “following” gear stage is then generally preselected in the inactive transmission section, allowing a gear change from the source gear stage to the following gear stage to be performed by overlapping actuation of two friction clutches.
For automated shift transmissions and dual clutch transmissions, it is also a known practice to provide a dedicated actuator for each of the shift rods, allowing the shift clutch packs to be actuated independently of one another.
The practice of using shift drums to actuate shift clutches is furthermore known in the vehicle transmission sector. Here, the shift drums have a shift drum contour in which a driving feature connected to a shift fork engages in such a way that rotary motions of the shift drum can be converted into axial motions of the shift fork. A known practice in the area of dual clutch transmissions is to assign each transmission section a dedicated shift drum. However, it is also possible to operate the two transmission sections by means of just one single shift drum. In the latter case, disadvantages in terms of shifting time arise from the sequential shift sequence. Moreover, the resulting diameter of the individual shift drum is very large, and therefore the shift arrangement occupies a relatively large space within the transmission housing.